outbreak of severe vomiting in dogs associated with a canine … · alan d. radford, david a....

Population health data is lacking for companion animals such as dogs, cats, and rabbits, leav-ing a surveillance gap for endemic diseases and delayed detection of incursions of disease, such as equine influenza virus (H3N8) (1), avian influenza (H3N2) (2,3), and parvoviruses (3). In the absence of legislated programs of population surveillance, several attempts have been made to fill this gap

using secondary data, particularly from pet insur-ance providers (4). More recently, researchers have exploited the rapid digitization of electronic health records (EHRs) for passive surveillance. Data can be collected at great scale and analyzed in near–real time. EHR data are now routinely used in hu-man heath efforts (5–8), in which their timeliness, simplicity, and breadth of coverage complements surveillance based on diagnostic data (9,10). Such approaches are beginning to find healthcare value in veterinary species, especially among companion animals (4,11–13), a high proportion of which visit veterinarians (14).

In January 2020, one of the authors of this ar-ticle (D.G.), a primary care veterinarian in northwest England, contacted the other authors about seeing an unusually high number of cases (≈40) of severe vomiting in dogs; responses to a social media post suggested other veterinarians might have been ex-periencing similar events. Vomiting is a common complaint among dogs whose owners seek treat-ment for them (15,16). However, documented out-breaks are rare because established vaccines are available for most common known pathogens (17). In the absence of robust populationwide data, such sporadic reports frequently do not raise awareness of outbreaks.

For the response we describe, we obtained data from syndromic surveillance and text mining of EHRs collected from sentinel veterinary practices and diag-nostic laboratories, which we then linked with data from field epidemiology and enhanced genomic test-ing. In 8 weeks, using this approach, we described the temporal and spatial epidemiology, identified a pos-sible causative agent, and provided targeted advice to control the outbreak. Ethics approval was given by Liverpool University Research Ethics Committees (Liverpool, UK; VREC922/RETH000964).

Outbreak of Severe Vomiting in Dogs Associated with a Canine

Enteric Coronavirus, United KingdomAlan D. Radford, David A. Singleton, Chris Jewell, Charlotte Appleton, Barry Rowlingson, Alison C. Hale,

Carmen Tamayo Cuartero, Richard Newton, Fernando Sánchez-Vizcaíno, Danielle Greenberg, Beth Brant, Eleanor G. Bentley, James P. Stewart, Shirley Smith, Sam Haldenby, P.-J. M. Noble, Gina L. Pinchbeck

Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 27, No.2 February, 2021 517

Author affiliations: Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool Leahurst Campus, Neston, UK (A.D. Radford, D.A. Singleton, B. Brant, E.G. Bentley, J.P. Stewart, S. Smith, P.-J.M. Noble, G.L. Pinchbeck);Lancaster University Centre for Health Informatics, Lancaster, UK (C. Jewell, C. Appleton, B. Rowlingson, A.C. Hale); University of Bristol, UK (C.T. Cuartero, F. Sánchez-Vizcaíno); Animal Health Trust, Lanwades Park, Kentford, UK (R. Newton); The Liverpool Vets, Liverpool, UK (D. Greenberg); Centre for Genomic Research, University of Liverpool, Liverpool (S. Haldenby)

DOI: https://doi.org/10.3201/eid2702.202452

The lack of population health surveillance for com-panion animal populations leaves them vulnerable to the effects of novel diseases without means of early detection. We present evidence on the effectiveness of a system that enabled early detection and rapid re-sponse to a canine gastroenteritis outbreak in the Unit-ed Kingdom. In January 2020, prolific vomiting among dogs was sporadically reported in the United Kingdom. Electronic health records from a nationwide sentinel network of veterinary practices confirmed a significant increase in dogs with signs of gastroenteric disease. Male dogs and dogs living with other vomiting dogs were more likely to be affected. Diet and vaccination status were not associated with the disease; however, a canine enteric coronavirus was significantly associ-ated with illness. The system we describe potentially fills a gap in surveillance in neglected populations and could provide a blueprint for other countries.

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Methods

Data Sources

Veterinary Practices During March 17, 2014–February 29, 2020, we col-lected data from 7,094,397 consultation records (4,685,732 from dogs and 1,846,493 from cats) from EHRs from the Small Animal Veterinary Surveil-lance Network (SAVSNET), a volunteer network of 301 veterinary practices (663 sites) in the United Kingdom, recruited based on convenience (11). In brief, EHRs included data collected during indi-vidual consultations on species, breed, sex, neuter status, age, owners’ postcodes, and vaccination status. Each EHR is also compulsorily annotated by the veterinary clinician with a main presenting complaint (MPC) at time of visit, using a question-naire window embedded in the practice manage-ment system. Options for reasons for visit included gastroenteric, respiratory, pruritus, tumor, kidney disease, other unwell, post-op check, vaccination, or other healthy.

Given that severe vomiting was a key outbreak fea-ture, we undertook 2 complementary analyses. First, we used regular expressions to identify clinical narra-tives describing frequent vomiting, but excluded com-mon false positive search results (Appendix Table 1, https://wwwnc.cdc.gov/EID/article/27/2/20-2452-App1.pdf). Second, we used data on prescriptions to describe the frequency of all veterinary-authorized products containing the antiemetic maropitant (18). We calculated trend lines using Bayesian binomial generalized linear modeling trained on weekly preva-lence during 2014–2019 (19), which allowed us to iden-tify extreme (>99% credible interval [CrI]) or moderate (>95% CrI) observations.

Laboratories SAVSNET also collects EHRs from participating diagnostic laboratories on samples submitted from more than half of UK veterinary practices. Canine diagnostic test results from January 2017 through February 2020 were queried from 6 laboratories for 6 gastroenteric pathogens. Test numbers, percentage of positive results, and associated 95% CIs were summarized (Table 1). The number of sites was surmised from the submitting practices’ postcodes.

QuestionnairesOnline questionnaires to enable case reporting were made available to both veterinarians and owners beginning January 29, 2020. The required case definition of >5 vomiting episodes in a 12-hour period was based on clinical observations of early cases. Veterinarians were also asked to complete control questionnaires. Initially, we requested only controls matched to veterinary practices contributing case data; however, to increase recruitment, a nonmatched control questionnaire open to any veterinarian was deployed on February 5. The questionnaires (Appendix) requested a range of information including owner postcode, animal signalment, vaccination status, clinical signs, treatment and diagnostic testing, animal contacts, diet, and recovery status.

We performed all statistical analyses using R ver-sion 3.6.1 (https://cran.r-project.org). Case details were described for both veterinarian- and owner-reported data. We calculated proportions and 95% CIs for categorical variables and median and range for continuous variables. We constructed univari-able and multivariable mixed-effects logistic regres-sion models using data submitted by veterinarians using R package lme4. Explanatory variables from univariable logistic regression were considered in

518 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 27, No.2 February, 2021

Table 1. Results of laboratory diagnostic tests for pathogens associated with gastroenteric disease in dogs for samples collected during January 2017–February 2020, United Kingdom*

Pathogen Method No. tests No.

laboratories† Unique sites‡

% Positive (95% CI)

Peak month, % positive (95% CI)

CeCoV PCR 5,167 4 839 20.69 (19.58–21.79)

2020 Feb, 34.8 (27.81–41.85)

Canineparvovirus PCR 5,499 6 965 6.62 (5.96–7.28) 2017 Nov, 13.28 (7.38–19.18)

Giardia PCR 5,636 6 894 23.78 (22.66–24.89)

2018 Jan, 33.96 (26.58–41.35)

Salmonella spp. Culture 114,722 6 2,951 0.87 (0.81–0.92) 2018 Nov, 1.28 (0.87–1.70)

Campylobacter spp. Selective culture 111,983 6 2,947 16.10 (15.88–16.31)

2017 Dec, 23.02 (21.44–24.60)

Clostridium perfringens Enterotoxin PCR 5,138 3 2,947 16.10 (15.88–16.31)

2017 Dec, 23.02 (21.44–24.60)

*CeCoV, canine enteric coronavirus. †Number of diagnostic laboratories contributing test results. ‡Number of unique veterinary practices sites submitting samples to the laboratories.

Severe Vomiting in Dogs, United Kingdom

multivariable models for likelihood ratios of p≤0.20, which underwent manual stepwise backward elimi-nation to reduce Akaike’s and Bayesian information criteria. Practice was included as a random effect. We assessed confounding by the effect on model fit with sequential removal of variables and assessed 2-way interaction terms for improved model fit. We defined final statistical significance as p 19 bp matching the dog genome (CanFam3.1, http://genome.ucsc.edu) using Bowtie2 sequence align-ment tool (http://bowtie-bio.sourceforge.net) were removed. Remaining reads were assembled using the SPAdes toolkit (https://github.com) and con-tigs >700 nt blasted against the NCBI RefSeq nonre-dundant proteins database (https://www.ncbi.nlm.nih.gov/refseq). Sequences matching CeCoV were aligned using the ClustalW multiple sequence align-ment program (https://www.genome.jp) and phy-logenies reconstructed using bootstrap analyses and neighbor-joining in MEGA6 software (https://www.megasoftware.net). Each sequence was assigned a lo-cal laboratory number based on the order in which the sequences were analyzed.

Results

Syndromic Surveillance On the basis of MPCs identified in the EHRs, we found a specific and significant increase in the number of dogs recorded as exhibiting gastroenteric signs; the final 10 weeks, during December 2019–March 2020, were outside the 99% CrI (extreme outliers; Figure 1, panel A). A similar trend was observed in maropitant therapy for dogs (Figure 1, panel B). Both measures, peaked in the week ending February 2, 2020, at approximately double the preceding baseline. We observed no similar trends for respiratory disease in dogs, for gastroenteric MPCs, for maropitant treatment in cats (Figure 1, panels C–E), or for antibiotic use in dogs (data not shown), together suggesting the signal was specific to canine gastroenteric disease, a finding supported by similar increases in the regular expression identifying vomiting dogs (Figure 1, panel F).


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Spatiotemporal mapping of weekly cases of gas-troenteric MPC showed prevalence was spatially clustered (Figure 2). In particular, locations in north-west and southwest England and in Edinburgh, Scot-land, had strong evidence of many weeks of preva-lence higher than the national mean.

Diagnostic Tests The patterns of test results for different PCR tests, generally carried out concurrently, were broadly similar (Figure 3, panels A–C). The same was true for results based on cultured samples (Figure 3, panels D, E). Of particular interest, CeCoV showed strong seasonality, positive tests peaking during the winter months (Figure 3, panel A). However, similar peaks seen in previous years suggested the observed peak in February 2020 could not itself explain this outbreak.

Questionnaire By March 1, 2020, a total of 1,258 case questionnaires had been received. After excluding 59 questionnaires missing key data, we used data from 165 veterinary-reported cases, 1,034 owner-reported cases (Table 2), and 60 veterinary-reported controls (Appendix Table 2) for analyses.

Most cases were from households in England (Table 2). Median case age at examination was 4.0 years (range 0.3–15.0 years) based on veterinary re-ports and 4.8 years (range 0.2–15.5 years) based on owner reports. Most animals had been vaccinated against core pathogens (17) and leptospirosis within the preceding 3 years and dewormed within the pre-vious 3 months. A range of breeds (data not present-ed) were observed, broadly corresponding to previ-ous studies (6). Most cases were fed dog food, but


Figure 1. Observed prevalence of main presenting complaint (MPC) and maropitant use in cats and dogs, per 1,000 consultations, in investigation of dogs with vomiting, United Kingdom, January 2017–February 2020. A) Canine records labeled as gastroenteric MPC; B) canine records in which maropitant was prescribed; C) canine records labeled as respiratory MPC; D) feline records in which maropitant was prescribed; E) feline records labeled as gastroenteric MPC; and F) frequent vomiting in dogs based on regular expression searches of the clinical narratives. Red points represent the extreme outliers (outside the 99% credible interval [CrI]), orange points the moderate outliers (outside the 95% CrI, but within the 99% CrI), and green points the average trend (within the 95% CrI).


≈20%–37% of dogs scavenged food when walked. Of those from multidog households, just over half reported the presence of another dog recently vom-iting within the same household. Around 30% of dogs had recently traveled, most commonly visiting a daycare facility.

Date of onset of clinical signs ranged from No-vember 16, 2019, through February 28, 2020, for veter-inary-reported cases, and September 4, 2019, through March 1, 2020, for owner-reported cases. Most cases involved inappetence (75.6%–86.1%) and vomiting

without blood (88.7%–91.5%) (Table 3). Approxi-mately half of cases reported diarrhea, most without blood. Diagnostic testing was performed in 32.1% of veterinary-reported cases, most (78.9%) using hema-tology or biochemistry assays, or both.

Dogs in >90% of veterinary-reported cases were treated, compared with in 61.7% of owner-reported cases. In both, antiemetics were most often prescribed: in 89.1% (CrI 84.3%–93.9%) of veterinary-reported cases and in 48.1% (CrI 45.0%–51.1%) of owner-re-ported cases. The most common recovery time was


Figure 2. Rates of gastroenteric veterinary consults for dogs during November 4, 2019–March 21, 2020, in investigation of dogs with vomiting, United Kingdom. Consults were geolocated to owners’ postcodes, with gastroenteric main presenting complaint as a binary outcome (1 for gastroenteric consult, 0 for a nongastroenteric consult). Colored areas represent the number of weeks a given location had a 95% posterior probability of prevalence exceeding the national mean prevalence in any week. The geostatistical modeling approach used is further detailed in the Appendix (https://wwwnc.cdc.gov/EID/article/27/2/ 20-2452-App1.pdf).

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3–7 days; the dogs died in 0.6% of veterinary-report-ed and 1.0% of owner-reported cases.

Descriptive data about the control population, submitted by veterinarians, and univariable find-ings from analyses of the veterinary case controls are presented in Appendix Tables 2 and 3; multivariable findings are shown in Table 4. Both neutered and non-neutered male dogs were at significantly increased odds of contracting the illness, compared with neu-tered females, as were dogs living in the same house-hold as another dog that had also been vomiting com-pared to those in households where other dogs were healthy. However, dogs living in a single-dog house-hold were at increased odds of contracting the illness compared with dogs living in the same household as another dog that had not recently vomited. Dogs that had been in recent contact with another animal spe-cies (including humans) that had recently vomited were at reduced odds of vomiting, compared with those who had not. Other potential causes considered early in the outbreak, including foodborne etiologies, vaccine preventable diseases, or the possibility of in-terspecies transmission, were not significantly associ-ated (Appendix Table 3).

Sampling and Molecular Testing During January 30–March 12, 2020, we collected a total of 95 samples from 71 animals (50 cases, 21 controls): 22 from feces, 60 from oral swabs, and 13 from vomit. Dogs with prolific vomiting were signif-icantly more likely to test positive for CeCoV in >1

sample (17/50, 34%) compared with controls (0/21) (p = 0.002 by Fisher exact test). Positive test results were most likely in samples from feces (10/16 [62.5%] cases, 0/6 controls; p = 0.01) and vomit (6/13 [46%] cases, 0 controls). Samples from oral swabs were least likely to test positive (7/43 [16%] cases, 0/17 controls; p = 0.17). Of 17 CeCoV-positive cases, 12 met the case definition, 2 did not (


matched a canine rotavirus (1 case, 1 control; data not presented). Consistent with M-gene sequencing, 5 of the CeCoV genomes clustered together (>99% simi-larity), distinct from the genome from dog 15 (Figure 4). The outbreak strain was most similar to a virus from Taiwan isolated in 2008 from a young dog with diarrhea (94.5% similarity; L. Chueh, pers. comm. [email] Apr. 27, 2020) and did not show any obvious sequence differences to published strains that might explain the unusual pattern of disease observed in the outbreak. Based on spike gene analyses, the outbreak

strain clustered with IIb, having a TGEV-like N-ter-minal spike domain (23). Sequences were submitted to GenBank (accession nos. MT877072, MT906864, and MT906865).

DiscussionUsing EHRs annotated with syndromic information by veterinarians, we rapidly identified an outbreak of canine gastroenteric disease that had started in No-vember 2019. This finding was corroborated by par-allel increases in relevant prescriptions and records


Table 2. Veterinary- and owner-reported case questionnaire responses pertaining to signalment, health history, contacts, and feeding habits among dogs with vomiting, United Kingdom, January 2017–February 2020*

Question Veterinarian-reported cases, n = 165

Owner-reported cases, n = 1,034

% Responses (95% CI) No. unknown % Responses (95% CI) No. unknown Veterinary practice location England 80.6 (74.6–86.7) NA 89.8 (87.9–91.6) NA Wales 12.1 (7.1–17.1) NA 4.5 (3.2–5.7) NA Scotland 4.9 (1.6–8.1) NA 4.5 (3.2–5.7) NA North Ireland 1.2 (0.0–2.9) NA 1.1 (0.4–1.7) NA Republic of Ireland 1.2 (0.0–2.9) NA 0.1 (0.0–0.3) NA Isle of Man 0 NA 0.2 (0.0–0.5) NA Sex F 42.4 (34.9-50.0) NA 43.7 (40.7-46.7) NA M 57.6 (50.0–65.1) NA 56.3 (53.3–59.3) NA Neutered‡ 69.1 (62.0–76.2) NA 70.1 (67.3–72.9) NA Intact‡ 30.9 (23.8-37.9) NA 29.9 (27.1-32.7) NA Vaccinated within past 3 y† 94.6 (91.1–98.0) NA 88.4 (86.5–90.4 13 Distemper 92.7 (88.8–96.7) NA 49.7 (46.7–52.8) NA Infectious hepatitis 92.1 (88.0–96.2) NA 40.4 (37.4–43.4) NA Parvo 92.1 (88.0–96.2) NA 55.4 (52.4–58.5) NA Parainfluenza 53.9 (46.3–61.6) NA 37.4 (34.5–40.4) NA Leptospirosis 92.7 (88.8–96.7) NA 49.2 (46.2–52.3) NA Kennel cough 46.7 (39.0–54.3) NA 40.4 (37.4–43.4) NA Rabies 2.4 (0.1–4.8) NA 1.3 (0.6–1.9) NA Herpes 0.6 (0.0–1.8) NA NA NA Dewormed within past 3 mo 86.2 (80.5–92.0) 27 69.8 (67.0–72.7) 50 Lives in multidog household 34.6 (27.3–41.8) NA 47.4 (44.3–50.4) NA >1 dogs in household vomited 54.4 (41.3–67.4) NA 55.9 (51.5–60.3) NA Regular contact with other species† 54.9 (46.1–63.8) 43 44.1 (41.1–47.1) NA Cats 64.2 (52.6–75.8) NA 62.3 (57.8–66.7) NA Horses 20.9 (11.1–30.7) NA 28.3 (24.2–32.4) NA Cattle or sheep or both 25.4 (14.9–35.9) NA 22.2 (18.3–26.0) NA Pigs 3.0 (0.0–7.1) NA 1.5 (0.4–2.7) NA Poultry 13.4 (5.2–21.7) NA 14.0 (10.8–17.2) NA Rabbits 7.5 (1.1–13.8) NA 5.7 (3.6–7.8) NA Other species 11.9 (4.1–19.8) NA 20.6 (16.9–24.3) NA Contact with other vomiting species 13.5 (7.1–19.9) 54 17.4 (14.6–20.2) 320 Recent travel history† 31.4 (23.0–39.8) 47 26.7 (24.0–29.4) NA Boarding kennel 8.1 (0.0–17.0) NA 9.1 (5.7–12.5) NA Group training/behavior classes 24.3 (10.3–38.3) NA 35.5 (29.9–41.2) NA Doggie day care facility 48.7 (32.3–65.0) NA 39.5 (33.7–45.3) NA Overseas 2.7 (0.0–8.0) NA 0.7 (0.0–1.7) NA Rescue kennel 0.0 (0.0–0.0) NA 0.4 (0.0–1.1) NA Other 18.9 (6.1–31.7) NA 20.3 (15.5–25.0) NA Provided known food type† 95.2 (91.9–98.4) 8 100.0 (100.0–100.0) NA Proprietary dog food 95.5 (92.3–98.8) NA 85.9 (83.8–88.0) NA Home-cooked diet 6.4 (2.5–10.2) NA 10.4 (8.6–12.3) NA Raw meat 5.1 (1.6–8.6) NA 15.9 (13.6–18.1) NA Table scraps 14.7 (9.1–20.2) NA 16.1 (13.8–18.3) NA Scavenged food 36.6 (28.7–44.4) 20 19.9 (17.4–22.4) 24 *NA, not available. ‡Includes both female and male animals. †Multiple responses for the same dog are possible.

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of frequent vomiting. Those data were augmented by data from responses to a questionnaire, diagnostic laboratories, and enhanced microbiological analyses. This system enabled us to determine case definitions and outcomes and to identify risk factors as well as a potential viral cause, within a 3-month period; findings were rapidly disseminated to veterinarians (24,25) and owners. This combined approach repre-sents an efficient system that can fill a previously ne-glected national population health surveillance need for companion animals.

The first indication of an outbreak came from time-series analyses of syndromic data. Such syn-dromic surveillance is increasingly being used to monitor the impact of national events like natural di-sasters and bioterrorism on human population health, as well as changes in gastroenteric and influenza-like

illness (6–9). Such data can be simple to collect, pro-vide real-time wide geographic coverage, and be flex-ibly applied to different conditions (10,11). Although in some cases these data can identify outbreaks earlier than more active surveillance, their predictive value can sometimes be low, particularly where there is a low signal to noise complaint ratio. In our case, the outbreak was large compared with background lev-els, associated with near doubling of the gastroenteric syndrome, and had many weeks in which the syn-drome statistically exceeded the baseline.

The richness of data within EHRs enabled us to validate this outbreak using numbers of antiemetic prescriptions and text mining. Prescription data have been used to understand, for example, human health inequalities (26), and the use of critical antimicrobi-als in both humans (27) and animals (28,29). We used


Table 3. Veterinarian reported and owner-reported case questionnaire responses pertaining to clinical signs, diagnostic and management strategies, and case recovery likelihood and time among dogs with vomiting, United Kingdom, January 2017–February 2020*

Question Veterinarian-reported cases, n = 165

Owner-reported cases, n = 1,034

% Responses (95% CI) No. unknown % Responses (95% CI) No. unknown Clinical signs Vomiting without blood 91.5 (87.3–95.8) NA 88.7 (86.8–90.6) NA Vomiting with blood 8.5 (4.2–12.8) NA 11.3 (9.4–13.3) NA Diarrhea without blood 37.0 (29.6–44.4) NA 46.2 (43.2–49.3) NA Diarrhea with blood 10.9 (6.1–15.7) NA 12.3 (10.3–14.3) NA Melaena 1.8 (0.0–3.9) NA NA NA Pyrexia 12.7 (7.6–17.8) NA 15.4 (13.2–17.6) NA Inappetence 86.1 (80.8–91.4) NA 75.6 (73.0–78.3) NA Weight loss 18.2 (12.3–24.1) NA 34.9 (32.0–37.8) NA Lethargy 9.1 (4.7–13.5) NA 6.3 (4.8–7.8) NA Diagnostic testing performed 32.1 (25.0–39.3) NA 18.3 (15.9–20.7) NA Treatment provided to dog 92.1 (88.0–96.2) NA 61.7 (58.7–64.7 13 Recovery status known 88.5 (83.6–93.4) 19 98.4 (97.6–99.1) 17 Recovery


these data to identify and track an outbreak, benefit-ting from a clear link between the syndrome (vomit-ing) and its therapy (antiemetic). It will be useful to identify other disease-therapy associations that could be used for similar surveillance.

We used text mining to identify records of fre-quent vomiting in clinical narratives. Such approach-es can circumvent the need for practitioner-derived annotation and be flexibly and rapidly adapted to emerging syndromes as soon as case-definitions are determined. Similar approaches have been described in human health for conditions such as fever (30–32) but can suffer low sensitivity (31). Indeed, the out-break peak based on text mining was ≈20% of that based on MPC analysis. However, it is also likely the outbreak as defined by the MPC included a consider-able number of animals with milder signs that would not be detected by data mining using the regular ex-pression developed here. Although data from text

mining are unlikely to give an accurate estimate of the true prevalence of a given condition, they can still be used to track outbreaks.

To compliment syndromic surveillance, we implemented a rapid case-control study, collecting >1,200 responses from veterinarians and owners in 4.5 weeks. There was no evidence for similar disease in people or other species. The timing of the outbreak as shown by case data was in broad agreement with our syndromic surveillance. Questionnaires from owners and veterinarians were in broad agreement on date of onset, geographic density, clinical signs, and recovery. These data informed targeted health messages posted online and on social media on Feb-ruary 28, 2020, 4 weeks after we first became aware of the outbreak.

Clearly, evidence of transmission driving the out-break was vital to providing disease control advice. Dogs in multidog households were more likely to


Figure 4. Phylogenetic analysis of canine enteric coronavirus strains, including locations were sequences were obtained, in investigation of dogs with vomiting, United Kingdom. Trees are based on nucleotide sequences for M-gene (final alignment 299 positions) (A) and whole genome (final alignment 26,564 positions) (B). Evolutionary analysis was performed using the neighbor-joining method. Bootstrap testing using 1,000 replicates was applied; only values >70 are indicated. Sequences identified in this study are indicated in blue (strain 1), red (strain 2), and green (strain 3). Asterisks (*) indicate samples from animals meeting the case definition. Each phylogeny included closest matches in GenBank, as well as representative published canine coronavirus, feline coronavirus, and transmissible gastroenteritis virus isolates. Scale bars indicate substitutions per site. C) Approximate geographic location of sequences obtained in this study, number- and color-matched to sequences shown in panels A and B.

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vomit if other dogs in the household were also affect-ed, suggesting either transmission between dogs or a common environmental source; these observations informed advice to the public around isolating affect-ed dogs. Of note, dogs in single-dog households were also at increased odds of being affected compared to multidog households where only a single dog was vomiting. Some authors have shown that dogs from single-dog households are walked more and there-fore could be at greater risk for infection (33). Factors affecting dog walking are clearly likely to be impor-tant for control of infectious disease transmission and should be explored further.

In addition to collecting epidemiologic data, we collected microbiological samples from cases and controls. Based on its known (34) and observed sea-sonality (Figure 3, panel A), we tested all samples for CeCoV. Cases were significantly more likely to show positive results both when all samples (oral swabs, feces and vomit) were considered or when just fe-cal samples were considered, suggesting a possible role for CeCoV in the outbreak. However, many case samples tested negative: 33 of 50 overall, 6 of 16 dogs for which feces samples were submitted, and 7 of 13 dogs for which vomit samples were submitted. There are several potential reasons for these negative find-ings, including the sensitivity of the PCR, the high numbers of oral swabs (although simpler to collect, oral swabs were more likely to test negative), the tim-ing of samples in relation to viral shedding, and the storage and transport of samples. In addition, it is important to note that our case definition, based as it was on a syndrome and lacking more specific con-firmatory testing, is likely to include some animals that were not part of the outbreak. Indeed, at its peak, the outbreak only doubled the background level of gastroenteric disease seen at other times of the year; therefore, we might expect only half of our cases to be truly associated with the outbreak.

Sequencing results identified a predominant CeCoV strain in outbreak cases across the United Kingdom, in contrast with earlier studies showing that CeCoV strains tend to cluster in households, veterinary practices, or lo-cal areas (35). This finding lends further support to the role of this strain in the observed outbreak. In Sweden, a single strain was also implicated in several small winter-time canine vomiting outbreaks (36); genetically, how-ever, the virus strain we identified was distinct from the strain from Sweden (data not shown). Ultimately, it will be necessary to perform a challenge study to confirm or refute the role of this CeCoV strain as the cause of this outbreak, as well as to explore the range of clinical signs associated with infection.

If this strain is proven to be the cause of the out-break, several features mark the observed pattern of disease as unusual, including the outbreak scale, its geographic distribution, the severity of signs in some animals, a lack of notable viral co-infections, and the involvement of adult dogs. CeCoV is generally asso-ciated with mild gastroenteritis (37). Although spo-radic outbreaks of more severe hemorrhagic diseases with high mortality (38–40), as well as systemic dis-eases (41,42), have been reported, these typically af-fect individual households, and are often associated with mixed infections (43). Such observations sug-gest that the genetic variability of CeCoVs may affect virulence and are supported by experimental infec-tions recreating more severe disease (38). The genetic mechanism underlying such shifts in virulence in CeCoV have not been defined. However, mutations impacting virulence are described in closely related alphacoronaviruses (44–47).

In conclusion, this multidisciplinary approach en-abled a rapid response to a newly described outbreak of canine gastroenteritis and identified a CeCoV as a potential cause. Previous CeCoV seasonality suggests further outbreaks may occur. Having such an efficient surveillance system provides the ideal platform to in-form and target population health messaging. Several challenges remain for addressing the lack of national population health structures for companion animals: to systematically capture discussions of disease in social and mainstream media; to sustainably fund these activi-ties, which currently are largely resourced by research grants; to understand and broaden the representative-ness of such sentinel networks; and to link surveillance information with agencies empowered to act (12).

AcknowledgmentsWe thank data providers both in veterinary practice (VetSolutions, Teleos, CVS Group, and independent practitioners) and participating veterinary diagnostic laboratories (Axiom Veterinary Laboratories, Batt Laboratories, BioBest, Idexx, NationWide Laboratories Microbiology Diagnostics Laboratory at the University of Liverpool, the Department of Pathology and Infectious Diseases at the University of Surrey, and the Veterinary Pathology Group), without whose support and participation this research would not have been possible. We are especially grateful for the help and support provided by SAVSNET team members Susan Bolan and Steven Smyth.

This work was funded in part by the Dogs Trust as part of SAVSNET-Agile, and by the Biotechnology and Biological Sciences Research Council, and previously by the British Small Animal Veterinary Association.



About the Author Dr. Radford is a professor of veterinary health informatics at the University of Liverpool. His primary research interests are the molecular epidemiology of viral pathogens, particularly those of veterinary importance, and combining this subject with electronic health data to study animal diseases at a population level and their impact on people.

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Address for correspondence: Alan Radford, University of Liverpool, Leahurst Campus, Chester High Road, Neston, S. Wirral, CH64 7TE, UK; email; [email protected]


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